1. Field of the Invention
The present invention relates to the field of protein and peptide chemistry.
2. Disclosure of the Related Art
Conventional methods for modifying the C-terminal of a protein or peptide, using a compound containing a nucleophilic group such as an amino group, hydroxyl group, or thiol group, have involved using a material such as 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC) or N-hydroxysuccinimide (NHS) to effect an active esterification of the C-terminal of the protein or peptide, and then conducting a reaction with an amino group. However, these reagents also react with side chain carboxyl groups contained within aspartic acid residues or glutamic acid residues in the protein or peptide, meaning that in order to ensure selective modification of the C-terminal, the side chain carboxyl groups of these amino acid residues must first be protected.
Japanese Laid-open Patent Publication No. 10-293130 (1998) discloses a method of determining the amino acid sequence from the C-terminal of a protein or peptide by converting the C-terminal of the protein or peptide to an oxazolone, liberating the C-terminal amino acid, and then repeating the operation of separating and identifying the produced amino acid.